Security devices in the form of tags that can be attached to merchandise in EAS systems are widely used to alert retailers to unauthorised removal of tagged merchandise from their premises.
Some types of EAS tags can be activated to prevent unauthorised removal and can be deactivated when removal of the tagged article from premises is permissible. And example of the use of such a system is in libraries, where tags containing magneto-harmonic markers (also known in the art as “sensors”) are magnetised to deactivate the tags when a book may leave the library and are demagnetised to activate the tags upon the book's return, to prevent unauthorised removal of the book.
Another type of EAS device is known as a “hard tag” and includes a rigid body housing an EAS sensor and a tack. The tack has a shank with a sharp end that can pass through an article of merchandise and that can be received in an aperture in the tag body, where it is held firmly to prevent removal of the tag from the article of merchandise. When the merchandise may legitimately leave the premises under surveillance, the tag is removed from the article of merchandise with a purpose-built detacher, which releases the tack to be withdrawn from the body. The EAS tag can be configured as a disposable or re-usable tag.
Hard tags of this type are intended to be kept on the premises and are removed from merchandise that may leave the premises, with the result that it is not necessary and is generally undesirable to deactivate the tags. However, hard tags that are presently used typically include an acousto-magnetic (AM) sensor comprising of an amorphous metal strip and a ferromagnetic strip alongside the amorphous strip, generating a magnetic field of a predetermined strength. The tags can be deactivated if the strength of the magnetic field can be altered sufficiently and this can be done by bringing a sufficiently strong magnet into proximity of the tag. Accordingly, it is possible for shoplifters to use strong magnets to deactivate these tags and to remove tagged merchandise from the premises undetected.
A solution to this problem was proposed in U.S. Pat. No. 6,348,865 (to Siegel), in which the ferromagnetic strip is replaced by two permanent magnets that are positioned in diagonally opposing positions at the ends of the amorphous metal strip. However, the use of two permanent magnets is costly.
Many EAS tags that are presently in use, can be removed from the articles of merchandise to which they have been attached, using heat (e.g. from a hand held cigarette lighter) to overcome the attachment means of the tag to the merchandise.
The present invention seeks to provide an EAS tag including a cost effective AM sensor that cannot be deactivated magnetically. The invention also seeks to provide an EAS tag that offers resistance to tampering with its attachment means using heat. The invention further seeks to provide an EAS tag that can house multiple sensors, preferably different types of sensors.